The lead accumulators that have been in use for decades as battery assemblies for motor vehicle onboard electrical systems exhibit a self-discharge, which if the vehicle has not been used over a period of several months, leads to a complete discharge and destruction of the battery. In order to make the vehicle operational again in such a case, a new battery has to be installed, which is associated with significant effort and costs. In particular, in vehicles that are produced for export and transported to the customer overseas, the time between when the vehicle was manufactured and when it was delivered to the customer can be so long, and the distances covered by the vehicle under its own power over this period can be so short, that the battery has experienced damage at the point it is handed over to the customer.
Many modern vehicles have electrical loads that normally remain in operation when the vehicle is parked and its motor is turned off, such as a remote controlled door unlocking device, an alarm system or the like. Such loads can also lead to a destructive exhaustive discharge even in a battery pack with a low self-discharge given an extended downtime.
Known in battery assemblies with lithium-ion cells is to provide an electrically controlled main switch, which can be used to separate the cells of the battery assembly from their terminals. Such a main switch may be necessary for safety reasons, so as to interrupt the flow of electricity given a short circuit in one of the loads supplied by the battery assembly, and thereby prevent overheating, which might cause the battery assembly to catch on fire. Such a battery pack can also be used for supplying the onboard electrical system in a motor vehicle, wherein a very long service life is possible for the battery with the main switch open, without there being any danger of an exhaustive discharge. In order to close the main switch again, however, it must be exposed to an electrical control signal that cannot be generated from the onboard electrical system of the vehicle if the latter is completely decoupled from the battery assembly. Introducing such a control signal from outside requires that a suitable signal source be present, which cannot be assumed in the case of an end user. However, even if battery packs in a large number of vehicles have to be reactivated, for example after a lengthy maritime transport, connecting a signal source and sending out the required signals is a time-consuming process.